Method and means for refining metals



r H. M. SHIIVIER.- METHOD AND MEANS FOR REFINING METALS.

APPLICATION FILED JAN. 26, i920- Patented Jan. 10, 1922.

sfeam ce i HERBERT IE. SHIMER, 01* PHILADELPHIA, PENNSYLVANIA.

METHOD AND MEANS FOR- BEFINING METALS.

Application filed January 26, 1920.

State of Pennsylvania, have invented an 1m;

provement in Methods and Means for Befining h/letals, of which the following is a specification.

The object of my invention is to provide a method and means for refining metals of relatively low fusibility and high volatility, whereby there shall be a substantially perfect refinement and minimum loss.

l-lereto'fore the refining of aluminum, zinc and similar metals and alloys thereof and especially in reclaiming aluminum from borings and other waste arising from machine work upon castings or other worn out castings, etc, has been attended with imperfect results and very considerable loss owing to the freedom with which they oxidize and volatilize. and it is an object of my invention to eliminate these objectionable results and thereby not only insure great saving by increasing the quantity of the recoveries, but also obtaining a cleaner and purer, prod uct as a result of my improved process In carrying out myimproved process. I fuse and melt within a crucible or furnace pot from which air is excluded, the metal or alloy to be treated: and during said meltmg subsequent treatment, prior to casting or drawing oil the product, subiecting the molten metal or alloy being treated to a suitable flux in an atmosphere which will prevent material oxidation and nreferablv insure a reducing influence upoii the mol ten metal during and preferably throughout the melting and refining operations.

My improved method and apparatus are more fully described hereinafter and de fined in the claims, the description being had in connection with the accompanying drawings, in which: i i

Fig. l. is a vertical section of a refining furnace embodying my improvements and in which to practice my improved process; and 2 is a transverse sectional view of the same, taken in a vertical plane in the direction of line of Fig. 1.

2 is the furnace proper. preferably made of firebrick and provided near the lower part with a suitable oil or gas burner 9 or other source of heat. The burner shown, comprises a mixer and jet producing body 9 Specification of Letters Patent.

Patented Jan. ill, 1%?22.

Serial No. 354,191.

having a controlled supply pipe 10 for oil or gas and a controlled blast pipe for compressed air or steam. 12 is a control valve for regulation of the burner as to the extent of the flame produced.

3 is a large crucible arranged within the furnace chamber and supported in an oblique position, such that its lower or bottom end is sustained upon the base or pedestal a of firebrick and its neck or throat 5 is extended through the front wall 14: at 15.

The lower and large body portion of the crucible extends through the opening 13 in the rear wall of the furnace, and near its lowest partit is provided with a casting aperture 7. which may be sealed with fire clav 8 during the melting and refining opei .tion and the seal broken when casting the content of the crucible.

The crucible is filled. or charged through the neck 5 and before the melting operation begins, the neck is filled with a stopper or fire clay plug and may be luted with fire clay sufficiently to prevent entrance of air into the crucible. or too free escape of the gases from within the crucible chamber 20. 17 are tuyeres fitted into apertures 19 formed in the upper part of: the crucible above the level of the liquid content thereof; and these tuyeres are connected with any form a continuation of superheating coil or manifold 16. through which steam or other gaseous medium is supplied to the tuyeres and under the control of a valve 18. I have found steam, when superheated in the coil 16. to be suitable for the atmosphere within the crucible or pot containing the molten metal and as a means to prevent 1nfiow of air. In practice the air within the crucible may be displaced with the steam as the preliminary operation and before or after the charge is introduced and the neck of the crucible is sealed. It is not'essential that the cruciblebe hermetically sealed as a reasonably tight sealing willinsure satisfactory and e'tlic-ient results, though, the best results may be obtained when the sealing is well made during the period in which the metal is in the molten condition.

The temperature to be provided by the burner 9 or other sourceof heat may be va ried according to the metal or, alloy to be melted and refined and I do not restrict myself in this respect.

By superheating the steam. in coil 16, it

is brought to a condition of dissociation when admitted to the crucible and, aside from its utilization in blowing outthe air from the crucible, the oxygen of the steam which remains is readily taken up by the carbon which may be present in the crucible,

whether from the graphite of the crucible itself, from carbon in the charge, or dissociated carbon from the oil mixed with the metal turnings or scrap constituting the metal element of the charge. The oxygen is thus converted into carbonic acid and remains as an inert part of the gaseouscontent of the crucible, or it may be absorbed in or combined with the fluxes introduced or slag produced according to specific employment of my invention. In any event, whether the carbonic acid remains as an inert gas or in any other combination, the reducing and quantity of it is not a material .matter aife'cting the refining operation.

The hydrogen dissociated from the oxygen of the steam provides a reducing atmosphereand protects the metal from combinaation withother elements which may be present. The oil present in the metal turnings or scrap being melted will provide hydro-carbons which may provide additional hydrogen in the event of its carbon becoming combined with the oxygen, as before pointed out. The result, in any event, is to provide a reducing atmosphere, within the crucible which is maintained throughout the refining process.

By sealing the crucible or melting pot during the melting and refining process, the volatile'vapors arising from the metals being treated are prevent-ed from escaping and as thegases also are prevented from escaping to an'eXtent which would freely admit the atmospheric air no losses in metal from this cause are permitted and hence the entire metal content of the charge remains and in sures-a maximum metal output possible.

By supplying superheated steam under ,pressure to the sealed crucible or melting pot, this pressure is exerted upon the molten mass and raises the volatilizing temperature and thereby permits the refining to be carried on efliciently at a higher temperature than that at which the metal normally volatilizes under atmospheric pressure. The result of this treatment at higher temperature is to secure better refining action and a purer product. The melting andrefining under a confined gaseous atmosphere incapable of injurious'efi'ect upon the metal content, enables the process to be carried on for any period desired without loss from escaping.

metallic vapors, or their conversion into compounds which enter the slag, and this feature of the invention is especially important.

- That the refining takes place in a reducing atmosphere is also of much importance,

sired, a further quantity of carbonmay be employed as a part of the charge and'incou porated with the flux,-which maybe of any usual character and suitable for-collecting the foreign substances to be removed from the metal being" refined. I have found that I during refining the addition of one-half to one per cent of crystal chloride and zinc as a flux to the charge will quickly cause the pasty aluminum mass to become fluid with the liberation of chlorin and under therefining process make the fluid aluminum separate to a position beneath the slag.

After the metal charge has been subjected to the preliminary refining temperature Withinthe confines of the crucible or vessel with the air blown out and while under the influence of the reducing atmosphere (pref? erably of a pressure above atmospheric pres sure), whereby the metal is melted and re duced to a clean andpure condition. The casting aperture? may be then opened by removing the scaling plug 8 and the pure metal completely cast, without disturbance and inferior results such as would result if the crucible were tilted to pour the metal from beneath the slag. After the metal has been fully run off, the slag may be east through the same orifice; and where thereis not an excess of slag, the same may remain in the crucible with the next heat without detriment. V. V V

While I have found that superheated steam is suitable for the atmospherewithin the crucible or melting vessel during refining, I do not confine myself thereto, as any inert gaseous medium may be employed, such as hydrogen, nitrogen, carbonic acid and carbonic'oXide, as examples. It will further be understood thata. suitable gas may be provided within the vessel'by supplying a medium as carbon, oil, grease or flux tothe charge before sealing and, after gasi'fying,

maintaining the pressure by steam or other gas supplied, byuthe tuyeres, either heated or otherwise, as desired. I i

While my process is particularly useful in recovering and refiningaluminum, it may be employed in the refining of zinc and all superi metals having a low volatilizing temperature or where volatile metallic compounds re formed and which would escape with except for the non-oxidizing atmosphere of the crucible or sealed compartment in which t ey are subjected to treatment.

1 have described my improved and means in that particularity which I deem to be. the h st exposition of my invention, and that which I prefer in commercial practice, but I do not restrict r confine mys lf to the minoi. or secondary details, as such variations may be resorted to as matters of mechanical skill and without a departure from the spirit of the invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is

l. The herein described process for recovery and refining of metals having low wlatility, which consists in confining the metallic charge including a reducing material within a melting vessel from which the atmosphere is substantially excluded, subjecting the vessel and its charge to a temperature sufficient to fuse the metallic charge to a pasty condition and while doing so introducing a gaseous atmosphere to prevent inflow of air, introducing a suitable flux capable of bringing the pasty mass to a fluid state at a higher temperature and during this action continuing the maintenance of the gaseous atmosphere to prevent inflow of air, and finally casting the metal separate from the slag.

The invention according to claim 1, wherein the charge includes carbon and the air is excluded from the vessel by an atmosphere therein com osed of gases of carbonaceous character, hydrogen and hydrocarbons resulting from the action of superheated steam upon the carbon of the charge.

3. The invention according to claim 1, further characterized by providing the metallic charge with carbon and supplying superheated steam to the vessel to blow out the air and in effect seal it against the entrance of air, and after heating the vessel to bring the metal to a pasty condition under a continued pressure in excess of atmospheric pressure during the refining operation, adding a chloride flux to bring the mass to a fluid condition.

at. l he invention according to claim 1, further characterized by providing aluminum scrap and carbon as the metallic charge, and crystal chloride of zinc as the flux to raise its temperature and render the charge fluid, vigorously stirring the fluid content of the vessel during the refining operation and at the same time maintaining the gases within the vessel at a pressure above atmospheric pressure. I

5. The process for refining metals, which consists in heating a metal to a temperature higher than its volatilizing temperature while confined within a closed vessel, maintaining a heated gaseous medium within the closed vessel above the molten metal to exclude atmospheric air during the fusing and refining operation, dr wing off the refined molten metal from the lower part of the vessel, and maintaining the atmosphere within the vessel at a pressure above atmospheric pressure during the drawing off or casting of the metal from the vessel to maintain the temperature and facilitate the cast ing flow of the metal.

6. The process of refining metals, which consists in melting a metal of low volatility within a sealed vessel and maintaining within the vessel a gaseous atmosphere above the molten metal having constituents which do not materially combine with the metal, maintaining the molten metal in the sealed vessel under continued pressure and at a temperature above its volatilizing temperature until it reaches a condition of refined purity, and thereafter casting the metal.

7. In a refining furnace, a stationary vessel having a body portion for containing the metallic charge to be refined, said vessel provided with a casting orifice at its upper part inclined to one side of the body portion, a furnace containing the body portion of the vessel and exposing both the charging orifice and the casting orifice, and n'ieans for maintaining a supply of a suitable gaseous medium to the upper part or the body portion of the vessel so as to be above the molten metal therein and also to one side of the charging orifice.

8. The invention according to claim. '7, further characterized by the vessel being formed of crucible shape, set obliquely across the furnace with its neck extending through the furnace wall and having a removable sealing plug, and the means for supplying the gas to the interior of the vessel comprising a tuyeres fixedly opening through the upper wall of the vessel and leading to a source of superheated gaseous medium outside of the furnace.

9. The invention according to claim 8, wherein the super-heating means comprise suitable coils within the furnace and having a tuyere connection opening through the upper wall structure of the vessel.

lii'testimony of which invention, I hereunto set my hand.

HER-BERT M. SHIMER. 

